Moistureproof sheet wrapping material



Patented Nov. 17, 1942 MOISTUREPBDOF SHEET WRAPPING MATERIAL Daniel D.Lanning, Williamsville, N. Y., assignor to E. 1. du Pont de Nemonrs aCompany, Wilmington, Del, a corporation of Delaware No Drawing.Application September 10, 1940, Serial No. 356,187

15 Claims. (CL 117-145) This invention relates to moistureproof sheetwrapping material, especially transparent nonfibrous moistureproofedcellulosic web. More particularly it appertains to odorless,self-anchoring moistureproofing coatings on films of regeneratedcellulose and the like.

Recently there has appeared in commerce a transparent moistureproofsheet wrapping material comprising a base sheet of regenerated cellulosehaving a thin moistureproofing coating. The moistureproofing coatingordinarily employed comprises essentially film forming (binding,cementing) material, for example, nitrocellulose, and moistureproofingmaterial, for example, a waxy substance such as paramn wax. The coatingmay also contain transparentizing (blending, homogenizing) materialand/or plasticizing material.

The manufacture of a typical non-fibrous base sheet is described in U.S. A. Patent'No. 1,548,864 (Brandenberger) and the coating thereof withtypical moistureproofing coating compositions is described in U. S. A.Patents No. 1,737,187 (Charch 8: Prindle), 1,826,697 (Charch a Craigue),and 2,147,180 (Ubben),

When products containing considerable water (cheese, fish, freshvegetables, etc.) are wrapped in the aforementioned sheet material, thesurface coating loosens in a few hours. As a result, the effectivenessof the wrapping is very appreciably reduced. A way of precluding orovercoming this failing is to anchor the moistureproofing coating to thebase sheet by means of an intermediate coat.

A simpler procedure in which some substance is incorporated in themoistureproofing coating composition, and applied therewith for thepurpose of anchoring the coating to the base, is obviously desirable.

It was an object of this invention to produce sheet wrapping materialshaving self-anchoring moistureproofing coatings. Another object was theproduction of a flexible, odorless, colorless, transparent,moistureproof sheet wrapping material comprising a regenerated cellulosefilm (pellicle, foil, sheet, tissue, web) having a selfanchoringmoistureproofing coating adhering tenaciously thereto even in thepresence of water. Further objects were to devise a simple processapplicable to existing and conventional equipment for causingmoistureproofing coatings to anchor themselves to regenerated celluloseand like film, to improve the anchorage of mois- 5 solution of:

vance in the art, and other objects which will appear hereinafter, arealso contemplated.

Surprisingly, it has now been found that resinous derivatives of amethylol urea ether will securely adhere moistureproofing' coatings notcontaining cellulose substitution derivatives as the principal filmforming material to regenerated cellulose film, and that the resultingmoistureproof sheet wrapping material is greatly superior to theproducts heretofore known.

From the following description and specific examples, in which aredisclosed certain embodiments of the invention, as well as details ofwhat is believed to be the best mode for carrying out the invention, itwill be apparent how the foregoing objects and related ends areaccomplished. The parts are given by weight throughout the applicationunless otherwise specified.

Example I A web of regenerated cellulose in gel condition, which hadbeen cast from viscous, desulfured, bleached and washed free fromimpurities in the conventional manner (U. S. A. Patent No. 1,548,864 toBrandenberger), was led through an aqueous softening bath containing4.33% glycerol. The gel film containing the glycerol softener was thendried in the usual manner by passage over heated rolls maintained at -90C,

After bringing the sheet material to norm humidity, it wasmoistureproofed by coating it with a coating composition consisting of a20% Per cent Urea formaldehyde monohydric alcohol (normal-butanol) resin(solids basis) 16.80

Chlorinated rubber (%68% Cl.) 37.0 Parafiln wax (M. P. 60 C.) 3.0Dibutyl phthalate 6.67 Dicyclohexyl phthalate 6.67Di-methylcyclohexyl-phthalate 6.66 Rosin 2,017,866 20.0 Maleic acid 3.2

This is a modified rosin repared by treating rosin in accordance with U.S. A. atent No. 2017,866. In general its properties are much the same asthose of rosin, but with the diiference that it has a molecular weightwithin the range of 5% to 400% greater than ordinary rosin in its purestate and hi her than that of are abietic acid. That it has a mel ngpoint (as dete ed by the capillary tube method) of about 0., and higherthan the melting point of pure abietie acid and of purified rosin whenin the resin state. That it is substantially free from combined sulfurand hardenin substances held in combination, and that it has an 10 inevalue lower than that of pure abletic acid.

in a solvent consisting of normal-butanol 15% and toluene The web waspassed continuously through the bath of the aforementioned compositionmaintained at 35 C., the excess coating material removed by scraping,and the coated sheet dried (the volatile solvents removed) at atemperature above the melting point of the wax. The base sheet was 450gauge and the coating on the final product was in an amount proportionalto two pounds for each 3,000 sq. ft. base sheet surface (this quantityincludes coating on both sides of the film). There resulted amoisture-proofed sheet of regenerated cellulose which was transparent,flexible, odorless, non-tacky and colorless. It retained itsmoistureproofing surface coating tenaciously even when in direct contactwith water and high proportions of moisture for prolonged periods oftime. It was admirably suited for wrapping material to be employed incontact with products containing large amounts of water (or moisture)such as butter, cheese, wet fish, frozen fishand the like. The wrappingmaterial performed its desired function as a wrapper for thesecommodities even when stored for long periods of time.

Example II Non-moistureproof regenerated cellulose sheet was coated inthe manner described in Example I with a moistureproofing compositionconsisting of a 20% solution of:

in a solvent consisting of isobutanol and toluene 85%. The product wasnon-tacky and had an excellent permeability value.

Example III Regenerated cellulose sheet was coated by the procedure ofExample I, with a moistureproofing coating composition consisting of:

Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resin(solids basis) 3.24 Maleic acid 0.36 n-Butyl methacrylate polymer 7.44Paramn wax (M. P. 60 C.) 0.36 Diphenyl laura 0.60 Toluene 74.80Isobutanol 13.20

The resulting moistureproof sheet wrapping material had superioranchorage and improved heat sealing properties. In this coatingcomposition considerable care had to be exercised to securecompatibility of the various solids and desirable characteristics in thesolvent composition.

Example IV Regenerated cellulose sheet was coated with a moistureproofing coating composition consisting of:

Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resin(solids basis) 3.24 Maleie acid 0.36 Beta-naphthol modified rubber2,158,530- 6.48 Parailin wax (M. P. 60 C.) 0.72 Dewaxed dammar 1.20Toluene 74.80 Isobutanol 13.20

An alkylated beta-naphthol in which rubber is the alkylating agent. Thisproduct was prepared according to U. S. A. Patent 2,158,530 (William CirThe resulting moistureproof sheet wrapping material had superioranchorage and improved heat scaling properties.

Example V acetyl 1%) 6.48 Parafiin wax (M. P. 60" C.) 0.72 Dewaxeddammar 1.20 Toluene 35.20 Isobutanol 12.30 Ethyl acetate 40.50

A polyvinyl alcohol butyraldehyde resin which may be prepared by themethods disclosed in U. S. A. Patent No. 2,162,678 (Robertson).Polyvinyl acetnls of this type are also disclosed in U. S. A. Patents2,035,939 and 2.036.092 (Morrison) and U. S. A. patent applicationSerial No. 307,081, filed December 1, 1939 (Hershberger). The resultingmoistureproof sheet wrapping material had superior anchorage andimproved heat sealing properties.

Example VI Regenerated cellulose sheet was coated with amoistureproofing coating composition consisting of:

Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resin(solids basis) 3.24 Maleic acid 0.36 Pliolite 6.48 Paraflin wax (M. P.60 C.) 0.72 Dewaxed dammar 1.20 Toluene 74.80 Isobutanol 1320""Iliolite" is a thermoplastic rubber derivative ordinarily containingup to about 1% chlorine made by con- (lensing rubber with a catalystsuch as tin tetrachloride (see Paper Trade Journal, page 96. February23. 1939, J. I. E. c. xxvI. and U. s. A. Patents No. 1,797,188,1,846,247, 1,853,334 and 2.052.391 The chemical structure is alsodescribed in Rubber Age, April, 1939, and J. I. E. c. XIX, 1033.

The resulting moistureproof sheet wrapping material had superioranchorage and improved heat sealing properties. The compatibility ofparafiln wax and Pliolite is outstanding. Similar results were obtainedwhen a normal amyl ether of dirnethylol urea was used instead of thecorresponding butyl ether.

Example VII Regenerated cellulose web was moistureproofed by theprocedure described in U. S. A. Patent No. 1,737,187 (Charch 8rPrindle), using a coating composition consisting of:

Well anchored moistureproof coatings resulted.

Example VIII Regenerated cellulose sheet was coated with amoistureprooilng coating composition consisting Per cent Ureaformaldehyde monohydric alcohol (iso-butanol) resin (solids basis) 3.24Maleic acid"; 0.36 n-Butyl methacrylate polymer 1.80 Nitrocellulose(11.0% N) 1.80 Dewaxed dammar 0.84 Paraflin wax (M. P 60 C.) 0.36Dlphenyl lauramide 3.60 Ethyl acetate 40.50 Toluene 35.20 Isobutanol12.30

The resulting moistureprooi sheet wrapping material had superioranchorage and improved heat sealing properties.

Example IX A web of regenerated cellulose in gel condition, which hadbeen cast from viscose, desulfur'ed, bleached and washed free fromimpurities and softened in the conventional manner was brought to normalhumidity, and moistureprooied by coating it with a coating compositionconsisting of:

Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resin(solids basis) 1.28 Nitrocellulose (11.05% N) 9 secs. (dry) 4.88Paraflln wax (M. P. 60 C.) 0.35 Dicyclohexyl phthalate 5.61 Hydrogenatedcastor oil phthalate 0.20 Isobutyl alcohol s 0.66 Toluene 28.04 Ethylacetate 52.77 Isopropanol 2.09 Ethanol 4.12

in the manner described in Example I. The final sheet had a permeabilityvalue of 13.

Example X Polyvinyl alcohol sheet of 450 gauge was coated in the usualmanner with a moistur'eprooiing composition consisting of:

Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resin(solids basis) 25.20 Nitrocellose (11.4% N) 32.0 Paraflin wax (M. P.) 60C.) 3.0 Dicyclohexyl phthalate 8.33 Dibutyl phthalate 8.33 Dimethylcyclohexyl phthalate -1--- 8.34 Beckacite 1118"; 10.0 Maleic acid 4.80

'Beckacite 1118 is an ester gum-rosln and maleic acld glyceride mixtureor complex having a melting range of 1l9-215 I". and an acid number of17-22. It is one of a series of related maleic anhydride modified estergum resins commercially available.

made up as a 12% solids dispersion in a mixture consisting of ethylacetate 46%, toluene 40% and isobutanol 14%. The product was non-tackyand had great resistance to the action of water.

Example XI moistureprooied by coating it with a composition consisting0!:

' m the manner described in U. s. A. Patent No.

1,737,187 (Charch and Prindle). Well anchored moistureproof coatingsresulted. Similar results were obtained with the corresponding amylether.

Example XII Regenerated cellulose sheet 0! 450 gauge was coated with amcistureproot composition consisting of Per cent Dimethylol urea octylether (partially polymerized) Maleic acid 0.4 Butyl phthalyl butylglycolate 3.6 Gum dammar 0.8 Paraflin wax (M. P. 61 C.) 0.4Nitrocellulose (11% N) 3.6 Ethyl acetate 40.5 Toluene 35.2 Isobutylalcohol 123 by the usual procedure, the coating being carried out at 140C. Well anchored moistureproof coatings resulted. The sheet materialcould be heat sealed.

Example XIII A web of regenerated cellulose which had been cast fromviscose, desulfured, bleached, washed, softened by passage through a 6%aqueous glycerol bath and dried, all in the usual manner, was coated onboth sides with a coating composition consisting of:

Per cent Urea formaldehyde monohydric alcohol (isobutanol) resinsolution (65% solution in isobutanol) 25.2 Nitrocellulose (11.4% N) 49.2Dicyclohexyl phthalate 9.0 Dimethyl cyclohexyl phthalate 9.0 Maleic acid4.8 Paraflln WM: 1.5 Dammar resin 1.3

The coating was applied from a 11.7% solids solution in a solventconsisting of:

Per cent Ethyl acetate 46.0 Toluen 40.0 Isobutyl alcohol 14.0

by passing the regenerated cellulose web through the bath and scrapingoi! the excess coating composition. The dip bath was maintained at atemperature high enough to prevent separation of the wax, before andafter application (35 C.) The coated sheet was dried at a temperatureabove the melting point of the wax (80 0.). The product wasexceptionally well suited for use as a milk bottle hood.

Similar results were obtained when volatile ester solvents such asisopropyl acetate and iso- Regenerated cellulose web of 450 gauge wasbutyl acetate, and ketone solvents such as ethyl Example XIV Regeneratedcellulose sheet was coated on both sides with a composition consistingof Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resinsolution (65% solution iso-butanol) 4.0 Para-toluene sulfonic acid 0.5Nitrocellulose (high viscosity) 0.5 Isobutyl alcohol 33.25 Toluene 28.50Ethyl acetate 33.25

Example XV Continuous sheet regenerated cellulose in gel state, whichhad been cast from viscose, desulfured, bleached and washed free fromimpurities in the usual manner in the casting machine, was impregnatedwith glycerol by passing it through an aqueous bath containing 6%glycerol. The excess solution was removed from the web by means ofsqueeze rolls which reduced the water content of the sheet to betweenthree and. four times the weight of the cellulose. It was then dried inthe usual manner upon heated rolls.

The resulting sheet material (softened with glycerol) wasmoistureproofed by coating it with a moistureprooflng coatingcomposition of the following formulation:

Per cent Urea formaldehyde monohydric alcohol normal butanol) resinsolution (60%- 65% solution in normal butanol) 3.0 Nitrocellulose (11.4%N) 8 sec. viscosity.. 4.5 Dibutyl phthalate 3.0 Maleic acid 0.5 Dewaxeddammar 0.8 Paraflln (M. P. 61 C.) 0.3 Ethyl alcohol 4.0 Butyl alcohol8.0 Toluen 28.9 Ethyl acetate 47.0

In applying the coating the sheet was passed through a bath of themoistureproofing coating composition, the excess coating compositionremoved by scraping (any other suitable means may be employed), and thecoated sheet dried :at a temperature above the melting point of the wax.The finished sheet was then conditioned to bring it to the desiredmoisture content. Conditioning (humidification or dehumidification) tobring the uncoated film to a specific moisture content is carried outjust prior to coating in some instances, for example, when the film as aresult of being stored for extended periods of time has a moisturecontent different from that desired at the beginning of the coatingoperation. The resulting product was a sheet of regenerated cellulosewith a moistureproofing coating which was consisting of:

substantially odorless, transparent, flexible and moistureproof. Byvirtue of the presence of the polymerized methylol urea ether resin inthe coating composition, the moistureproofing coating was anchored verysatisfactorily to the base sheet. When the finished product was indirect contact with water or was used as a wrapping directly in contactwith products containing large amounts of water or moisture such asbutter, cheese, wet or frozen fish, ice cream and the like, the coatingremained anchored for very substantial periods of time (a month ormore).

Example XVI The procedure of Example XV was carried out using amoistureproofing coating composition Per cent Urea formaldehydemonohydric alcohol (normal-butanol) resin (50% solution in normalbutanol) 20.0 Nitrocellulose (12.5% N) 30 sec. viscosity 4.3 Beckacite1118* 2.0 Tricresyl phosphate 3.5 Salicylic acid 1.0 Paraifin (M. P. 61C.) 0.7 Isobutyl acetate 39.3 Toluene 29.2

The procedure of. Example VIII was carried out, using a moistureprooiingcoating composition consisting of Per cent Urea formaldehyde monohydricalcohol (normal-butanol) resin selution (60%- 65% solution innormal-butanol) 7.2 11.4% nitrogen nitrocotton 4.2 Parafiln 0.6 Phthalicanhydride 0.48 Dewaxed dammar 1.2 Dibutyl phthalate 1.2 Ethyl acetate57.20 Toluene 26.40 Ethyl alcohol 1.52 The moistureproof sheet wrappingmaterial had excellent anchorag and odor characteristics.

Example XVIII Regenerated cellulose sheet was coated with amoistureproofing coating composition consisting of:

The resulting moistureproof sheet wrapping materlal had superioranchorage and improved heat sealing properties. The base sheet oi U. S.A. Patent No. 2,123,383 may also be used satisfactorily.

Example XIX Regenerated cellulose web was moistureproofed 2,147,180(Ubben), using a coating composition consisting 01:

Per cent Iauryl ether of dimethylol urea (partially polymerized) 3.2Maleic acid 0.4 Gum dammar 0.8 Paraflin (M. P. 61 C.) 0.4 Diphenyllauramide 3.6 Nitrocellulose (11% N) 3.6 Ethyl acetate 40.5 Toluene 35.2Isobutyl alcohol 12.3

A well anchored moistureproof coating resulted. The sheet material couldbe heat sealed.

Example XX Regenerated cellulose web was moistureproofed by theprocedure described in U. S. A. Patent No. 2,147,180 (Ubben) using acoating composition Example XXI Regenerated cellulose webwasmoistureproofed by the procedure described in U. S. A. Patent No.2,147,180 (Ubben), using a coating composition consisting of Per centIsobutyl ether of dimethylol urea (partially polymerized) 3.2 Maleicacid 0.4 Ethyl-phthalyl-ethyl-glycolate 3.6 Paraflin (M. P. 61 C.) 0.4Gum dammar 0.8 Nitrocellulose (11% N) 3.6 Ethyl acetate 40.5 Toluene35.2 Isobutyl alcohol 12.3

Well anchored moistureproof coatings resulted.

As shown by the foregoing-specific examples, anchored moistureproofingcoatings on regenerated cellulose and like film can be obtained byincorporating in the moistureproofing coating compositions thepolymerization derivative of monoand/or di-methylol urea alkyl ether.

By the expression anchor or equivalents (anchoring, anchored, etc.) ismeant the securing of the surface coating on the base in such a way thatthe resulting product will withstand the deleterious eiiects of water(or moisture). In other words, the surface coating will not loosenand/or flake of! from the water sensitive base film when the product isdirectly in contact with water for by the procedures described in U. S.A. Patent No.

appreciable and substantial periods of time (at least two days whenimmersed in water at 20 C.)

Whether a substance is an anchoring agent or not is easily determined,for example, by comparing the time of immersion in water required toloosen a moistureproofing coating containing the substance, with thetime required to bring about the same loosening with the coatingomitting the substance being tested (but otherwise having the sameproportions of ingredients).

The dimethylol urea ether component of the moistureproofing lacquer orcoating composition may consist of a single ether or a mixture oidifferent ethers. The ether type material may be in the monomeric and/orthe partially polymerized form. Partial or complete polymerization maybe efiected after the coating has been applied to the base sheet.

The preparation of the urea tormalydehyde monohydric alcohol reactionproduct resin solutions may be carried out in various ways. Preterredprocedures are described in detail in U. S. A. Patent No. 2,191,957dated February 27, 1940 (Edgar & Robinson). The methylol urea ethers maybe prepared according to the disclosures in U. S. A. Patents No.2,191,974 dated February 27, 1940, and 2,201,927 dated May 21, 1940,2,213,921 dated September 3, 1940, and 2,247,419 dated July 1, 1941(Sorenson) The amount of methylol urea ether material in themoistureproofing lacquer is preferably in the neighborhood of 5%, 2% to8% being a preferred range.

Monohydric alcohols for use as solvents, either alone or in admixturewith other solvents for the methylol urea and/or methylol thioureacondensation (or etherification) include methanol, ethanol, propanol,isopropanol, normal butanol, isobutanol, amyl alcohol, hexyl alcohol,lauryl alcohol, octyl alcohol, benzyl alcohol, cyclohexanol, andethylene chlorhydrin. The mono ethers or esters, for example, ethyleneglycol, its mono-acetate, its man-ethyl and mono-phenyl ethers, may alsobe used in this process.

The urea ether material should be substantially odorless after beinghardened (condensed, polymerized). In order to save time in completingpolymerization it is desirable to use incompletely polymerized resinousmaterial rather than the monomeric crystalline monohydric alcohol etherof methylol urea.

Better seat sealing is obtained with the high alkyl ethers (octyl,lauryl, etc.) of methylol urea. The heat sealing properties are improvedby incorporating amides (for example, diphenyl-lauramide,dimethyl-benzoyl benzamide, acetanilide, etc.) in the moistureproofingcoating.

The dimethylol ethers are preferred to the mono methylol ethers.

The moistureproofing coating compositions used to make regeneratedcellulose and other non-moistureproof type sheet materialsmoist'ureproof comprise essentially moistureproofing material (one ormore moistureproofing agents), binding material (one or more bindingagents, and the methylol urea ether anchoring material. One or moreagents for homogenizing the coat ing composition and one or more agentsfor plasticizing the coating composition, may be present if desired.

The wide variety of materials, moistureproofing agents, binding agents,homogenizing agents, plasticizing agents, catalysts, etc., for use inthe coating compositions, and the characteristics which render themsuitable in such a composition, are well known in the art and aredescribed in the patent art. Certain materials being preferred warrantthe special mention which follows.

The preferred binders include rubber, rubberlike materials, rubberderivatives (such as halogenated rubber, isomerized rubber, andhydrogenated rubber), ether linkage resins (resins resulting from thereaction of polyhydric phenols with aliphatic polyhalides and during theproduction of which ether linkages are formed), vinyl resins and likematerials capable of forming thin, self-supporting films (numerous othersuch materials are mentioned in the patent art).

Preferably the binding material is a non-cellulosic substance such as arubber derivative containing chlorine. The best results have beenobtained with chlorinated rubber of 65%-68% chlorine content. The alkylmethacrylates, particularly the n-butyl methacrylates, are also verysatisfactory for this purpose.

A material composed of 60% vinyl chloride and 40% vinyl acetate has beenfound to be suitable.

In the field of rubber derivative (that is, products made up of isopreneresidues and obtained from rubber by substituting and/or cross-linkingthe isoprene units-see Paper Trade Journal of February 23, 1939, pages1-3) and rubberlike material, special mention may also be made ofThermoprene (a thermoplastic unsaturated hydrocarbon described in detailby H. L. Fisher in Industrial and Engineering Chemistry, volume 19, No.12, page 1325), polymerized chloro-2- butadiene-1z3, Pliolite andPlioform (Pliolite and Plioform are thermoplastic rubber derivatives ofsubstantially the same chemical composition, and either may containtraces of chlorine).

The ether linkage resin formed by the reaction ofdihydroxy-diphenyl-propane and betabeta'-di-chloro-di-ethyl ether inthepresence of alkali, is preferred.

As the moistureproofing material, any wax (used generically to includewaxy substances like paraffin wax, as well as true waxes which aremonohydric alcohol esters of higher fatty acids) may be employed.Ordinarily paraffin wax melting above 50 C., or better, that melting at60 C. (and above) is preferred.

The homogenizing agents should be substances which increase thecompatibility of the binding material and the wax. Resins and gums arethe most satisfactory substances for this purpose so far tested. 7

The application of the moistureproofing coating may be accomplished inany suitable manner, such as by passing the base film through a bath ofthe coating composition, by spraying the composition on the base, etc.After application any excess of the coating may be removed in anydesired manner, such as by doctor knives, doctor rolls, etc. Variouscoating procedures are known to the art, and in the interest of brevityneed not be reviewed here.

Clearer films are obtained when the coated fihn is chilled rapidly afterevaporation of the solvent from the coating.

In the preferred embodiment of the invention regenerated cellulose andlike materials are coated with moistureproofing coating compositionscomprising waxy material, organic solvent soluble binding material,blending material, plasticizing material, and the dimethylol urea etherproduct, and it is applied from solution in organic solvent.

In preparing the solution type of coating compositions the constituentsare dissolved in a solvent (a single organic liquid or mixture ofliquids as is expedient) to give a clear, homogeneous solution which maybe smoothly applied to the surface of the base film (sheet, web or thelike) in a layer sufficiently thin that the solids (resulting fromevaporation of the solvent) will produce a layer in the neighborhood andpreferably not exceeding 0.0005 inch in thickness.

Not only should the solvents be selected to give a. clear, homogeneoussolution, but the solid constituents should be so blended (compounded)that a clear, transparent film results.

While it is possible in certain instances to use solvents (for theformulation of the moistureproofing lacquer) which will have a solventaction on the base sheet, this arrangement is preferably avoided. In thepreferred procedures the solvents selected for the moistureproofingcoating composition or lacquer ingredients are those which do not have aharmful effect upon the base sheet to which the moistureprooflng lacqueris to be applied. In such cases the coating composition will notpenetrate through the base sheet, and will normally result in a surfacecoating or covering.

Although procedures not employing polymerization catalysts are generallysatisfactory, in the preferred processes an acidic condensing agent isemployed in conjunction with the methylol urea ether material. Ingeneral such materials are more effective the lower the pH of theirsolution. Acidic condensing agents for the polymerization processes ofthe present invention are well known in the art, for example, acids suchas phosphoric, maleic, citric, lactic, acetic, trichloracetic, tartaric,oxalic, phthalic, and the like. Acid esters and half esters, and ti 11ktsuch as mono-isobutyl phosphate, dibutyl phosphate, mono-phenylphosphate (and generically acid esters of phosphoric acid), mono-butylphthalate, and monoethyl succinate, are satisfactory condensing agents,as are acid resins such as rosin and modified rosin (see U. S. A.Patents 2,017,866 and 2,147,180). Phosphorous pentoxide, shellac,Glyptal (alkyd) resins, and the like, may also be used.

As a base this invention contemplates any smooth, substantiallynon-porous, non-fibrous sheet, especially cellulosic film precipitatedfrom an aqueous cellulosic dispersion or solution or from solution in anorganic solvent (one or more organic liquids). This includes sheets ofregen erated cellulose whether precipitated from viscose (solutions ofcellulose xanthate), cuprammonium or any other aqueous solutions ordispersions of cellulose. It also includes sheets of cellulose ethersand esters precipitated from aqueous solutions or dispersions (U. S. A.Patent No. 2,123,883 to Ellsworth) such as glycol cellulose, celluloseglycolic acid, alkyl cellulose (preferably methyl or ethyl cellulose),cellulose phthalic acid, and other similar cellulosic products describedby these terms. These specific cellulose substitution derivatives justmentioned are usually grouped under the generic term low (or lowly)substituted cellulose ethers (and esters). In the language of the art,low substituted cellulose derivatives are those in which there is notmore than one mol of substitution per glucose unit.

The organic solvent soluble cellulose substitution products such ascellulose acetate, cellulose propionate, cellulose butyrate, celluloseacetopropionate, cellulose acetobutyrate, ethyl cellulose, benzylcellulose, ethyl benzyl cellulose, and other esters and ethers ofcellulose (particularly the organic acid esters and the alkyl ethers ofcellulose) which can be precipitated from solution of the cellulosicderivative in an organic solvent, are also included.

In addition to the cellulosic sheets or films, there may also bementioned those from gelatin, polyvinyl alcohol, rubber hydrochloride,vinyl resins and the like.

The composition of this invention can be applied to base materialscomprising cellulosic threads or fibers whether natural, such as cotton,linen, jute, ramie, hemp and the like, or synthetic fibers precipitatedfrom aqueous cellulosic dispersions or solutions, or from solutions ofcellulosic derivatives in organic solvents.

In order that the finished sheet wrapping material may be of the desiredsoftness, a softener such as glycerol may be incorporated in the basesheet.

The base sheet may be clear or dyed in appropriate colors.

Moistureproofness, moistureproofing and moistureproof materials andexpressions are defined in U. S. A. Patent No. 2,147,180 (Ubben). In theinterest of brevity the definitions are not repeated here. The terms andexpressions related thereto and employed herein are used in accordancewith such definitions.

Heat seal bond and heat seal bond strength are defined and a standardtest for their determination is given in U. S. A. Patent No. 2,147,180(Ubben). In the interest of brevity the definitions and test descriptionare not repeated here. The terms and expressions related thereto andemployed herein are used in accordance with such definitions anddescription.

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

1. Moistureproof sheet wrapping material comprising a base formed ofnon-fibrous base sheet coated with a moistureproofing coatingcomposition, said coating composition comprising halogen containingrubber derivative film former, wax and dimethylol urea ether resin.

2. The material of claim 1 when the film former is chlorinated rubber.

3. The material of claim 1 when the base sheet is regenerated cellulose.I

4. The material of claim 1 when the dimethylol urea ether is the butylether.

5. Moistureprooi sheet wrapping material comprising a base formed ornon-fibrous base sheet coated with a moistureproofing coatingcomposition, said coating composition comprising chlorinated rubber filmformer, moistureproofing agent, blending agent, and dimethylol ureaether resin.

6. Moistureproof sheet wrapping material comprising a base formed ofnon-fibrous base sheet coated with a moistureproofing coatingcomposition, said coating composition comprising chlorinated rubber filmformer, moistureproofing agent, plasticizer, and dimethylol urea etherresin.

7. A method of forming moistureproof sheet wrapping material whichcomprises incorporatin: an incompletely polymerized dimethylol ureaether in a moistureproofing coating composition and coating anon-fibrous base sheet with the coating composition.

8. Moistureproor sheet wrapping material comprising a regeneratedcellulose base sheet coated with a moistureproofing coating compositionconsisting oi:

said modified rosin having the same general properties as rosin, butwith the diflerence that it has a molecular weight within the range of5% to 400% greater than ordinary rosin in its pure state; that it has amelting point, as determined by the capillary tube method, above 80 C.and higher than the melting point of pure abletic acid and or purifiedrosin when in the resinous state; that it is substantially free fromcombined sulfur and hardening substances held in combination; that ithas an iodine value lower than that 0! pure abietic acid; and that ithas a molecular weight higher than that or pure abietic acid.

9. A method of forming moistureproot sheet wrapping material whichcomprises incorporating an incompletely polymerized dimethylol ureaether in a moistureproofing coating composition and coating aregenerated cellulose base sheet with the coating composition.

10. A method of forming moistureprooi sheet wrapping material whichcomprises incorporating an incompletely polymerized dimethylol ureaether in a moistureproofing coating composition and coating a polyvinylalcohol base sheet with the coating composition.

11. A method 01 forming moistureproof sheet wrapping material whichcomprises incorporating an incompletely polymerized dimethylol ureaether in a moistureproofing coating composition including chlorinatedrubber as cementing material and coating a non-fibrous base sheet withthe coating composition.

12. A method 01' forming moistureproof sheet wrapping material whichcomprises incorporating an incompletely polymerized dimethylol ureaether in a moistureproofing coating composition including butylmethacrylate po ymer as cementing material, and coating a non-fibrousbase sheet with the coating composition.

13. A method of forming moistureproof sheet wrapping material whichcomprises coating a regenerated cellulose base sheet with a coatcomposition consisting of:

Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resin(solids basis) 16.80 Chlorinated rubber Cl) 37.0 Parafiin wax (M. P. 60C.) 3.0 Dicyclohexyl phthalate 6.67 Dibutyl phthalate 6.67Dimethylcyclohexyl phthalate 6.66 Modified ros 20.0 Mal ic acid' 3.2

said modified rosin having the same general properties as rosin, butwith the difierence that it has a molecular weight within the range of5% to 400% greater than ordinary rosin in its pure state; that it has amelting point, as determined by the capillary tube method, above 80 C.

Parts Urea formaldehyde monohydric alcohol (iso-butanol) resin (solidsbasis) 3.24 Maleic acid 0.36 n-Butyl methacrylate polymer 7.44 Paraflinwax (M. P. 60 C.) 0.36 Diphenyl lauramide 0.60

15. A method of forming moistureprooi? sheet 20 wrapping material whichcomprises coating 9. polyvinyl alcohol base sheet with a coatingcomposition consisting oi:

I Per cent Urea formaldehyde monohydric alcohol (iso-butanol) resin(solids basis) 25.20 Nitrocellulose (11.4% N) 32.0 Paraflin wax (M. P.60 C.) 3.0 Dicyclohexyl phthalate 8.33 Dibutyl phthalate 8.33 Dimethylcyclohexyl phthalate 8.34 Beckacite 10.0 Maleic acid 4.80

said Beckacite being an ester gum-rosin and maleic acid zlyceridemixture or complex having a melting range 01 119-2i5 F. and an acidnumber oi. 17-22.

DANIEL D. LANNING.

